Optical objective



{SEARCH ROOM 3,029,895 r WHT Feb. 13, 1962. A. cox ETAI.

- OPTICAL OBJECTIVE Filed Dec. 8. 195a United States Patent 3,020,804 OPTICAL OBJECTIVE Arthur Cox, Park Ridge, and Irving C. Sandhack, Morton Grove, Ill., assignors to Bell & Howell Company, Chicago, 111., a corporation of Illinois Filed Dec. 8, 1958, Ser. No. 778,802 4 Claims. (Cl. 88-57) This invention relates to an optical objective, and more particularly to a four-component optical objective optically corrected.

An object of the invention is to provide a highly corrected optical objective of four simple components.

Another object of the invention is to provide an optical objective having a biconvex front lens and a biconcave second lens in front of the stop with a third positive meniscus concave toward'the stop and a rear positive meniscus convex to the stop.

Another object of the invention is to provide a compact objective having a field of view of at least fifty degrees with a flat field and distortion free.

Yet another object of the invention is to provide an objective having a front group of components from which light converges slightly and a rear positive component adjustable relative to the front group for adjusting the equivalent focal length of the objective with little effect on the high correction of the objective.

It is to be understood that the terms front" and rear as herein used refer to the ends of the objective respectively nearer the longer and shorter conjugates thereof.

In the drawing, the single FIGURE illustrates an objective forming one embodiment of the invention. The objective includes a front simple biconvex component 1, a second biconcave simple component 2., a third positive meniscus component 3 and a rear positive meniscus simple component 4 with the components 1 and 2 in front of stop or diaphragm 5, which is located between the components 2 and 3. The components 1 to 4, comprise lenses L to L having radii of curvature R to R axial thicknesses 1 to 1' and axial separations s; to s The component 4 is adjustable relative to the remaining components to vary the focusing distance of the objective while causing substantially no deterioration of the high correction of the objective.

The objective may be considered as comprising an intermediate biconcave component 2 with a positive front component 1 and a rear positive lens member or group divided into the components 3 and 4 with the positive components 3 and 4 meniscus and convex toward one another to have a minimum deviation of light rays from the optimum path, and the axial adjustment of the component 4 has virtually no elfect on the correction of the objective. The Abbe dispersion numbers of the positive components 1, 3 and 4 should be greater than that of the negative component 2 to provide a low Petzval sum.

For high correction, the objective should comply with the following inequalities wherein F designates the equivalent focal length of the objective, f; to f; the respective focal lengths of the components 1 to 4 and f +4 the equivalent focal length of the components 3 and 4:

To correct higher order coma and achieve balance of astigmatism, the objective should comply with the following inequality:

For correction of spherical aberration and coma, the objective should comply with the following inequality:

Preferred constructions of the objective conform substantially to the following tables in which dimensions are in terms of inches and n designates the refractive indices for the sodium D line and V the Abbe dispersion numbers, and s indicates the axial separation for focal ad ustments from five feet to infinity:

Example 1 [Equivalent focal length=1.376.f/gi:k focal length=1.088. Aperture R1=+.4957 L1 i1=.l06 rid-1.094 V=53.6

- ar=e.055 R:=1.000 I t:=.069 'Ild=1.621 V-36.2

r:=.097 R5=.7667 L; ta==.062 fla=1.651 V=55.8

8 =.025 $0 .057 R =+.9928 L t4=.069 'na=1.661 V=55.8

Example If [Equivalent local length=1.395. Back local length=1.119 to 1.076. Aperture 173.5]

R =|-.500 L t|=.108 na=1.694 V=53.5

8r=.056 Rs=-1.048 Lg t|=.070 nd=1.621 V=36.2 R=+.467

u=.119 R|=.775 L; ta=.063 m=1.694 V=53.5

ss=.020 to .063 I R =+.926 L4 t4=.070 m=1.694 V=53.5

Example III [Equlvalentl'ocallength=l.377. Back focallength=1.12to1.08. Aperture 173.5]

R =+.497 L ti=.106 nd=1.6968 V=56.2

81=.055 Rs=l.035 L: t2=.069 nFL621 V= 36.2 RF=+A60 ss=.l17 Rr=.769 L tz=.062 1la=1.6968 V=56.2

sr=.025 to .057 RF+.916 L4 h=.069 m=1.6968 V'-=56.2

The above described objectives are highly corrected, may be adjusted for focal lengths by moving only the rear component and, since the positive power of the group of lenses 3 and 4 behind the component 2 is divided, the convergence of rays of the component 3 is not great, whereby adjustment of the component 4 has little effect on correction of the objective.

While the invention is thus described, it is not wished to be limited to the precise details described, as changes may be readily made without departing from the spirit of the invention.

What is claimed is:

1. In an optical objective, proceeding from front to rear, a positive front component predominantly convex forwardly, a negative biconcave second component, a stop, a positive meniscus third component concave to the ron and an axially movable focusing positive meniscus rear component concave to the rear, and being further characterized in that the objective conforms substantially to the following inequalities in which R; to R designate the respective radii of curvature of the surfaces of the components starting with the rear surface of the front component and proceeding to the rear:

2. In an optical objective, proceeding from front to rear, a positive front component, a second negative component, a third positive meniscus component and a rear positive meniscus component, and further characterized in that said objective is constructed in substantial compliance with the following table in which dimensions are in terms of inches, and proceeding from front to rear, L to L designate the lenses, R to R the radii of curvature of the surfaces, t; to t the axial thicknesses, s to s the axial separations, n the indices of refraction for the D line and V the Abbe dispersion numbers:

3. In an optical objective, proceeding from front to rear, a front positive component, a second negative component, a third positive meniscus component and a rear 4 positive meniscus component, and further characterized in that said objective is constructed in substantial compliance with the following table in which dimensions are in terms of inches, and proceeding from front to rear, L to L designate lenses, R to R the radii of curvature of the surfaces, t to t; the axial thicknesses, s to s; the axial separations, n the indices of refraction for the D line and V the Abbe dispersion numbers:

4. In an optical objective, proceeding from front to rear, a front positive component, a second negative component, a third positive meniscus component and a rear positive meniscus component, and further characterized in that said objective is constructed in substantial compliance with the following table in which dimensions are in terms of inches, and proceeding from front to rear, L to L designate the lenses, R to R the radii of curvature of the surfaces, t; to t the axial thicknesses, s to .9 the axial separations, n the indices of refraction for the D line and V the Abbe dispersion numbers:

R,=+.497 L1 t1=.106 1H=L6968 V=56.2

' a1=.055 Rs=l.035 L, zl=.069 n4=1.621 V=36.2

Rt=+A aa=.1l7 Rl1=.769 L: t;=.062 'I'lfl=1.6968 V=56.2

Rfl=.489

a==.025 to .057 R1=+.916 L. t4=.069 m=1.6968 V=56.2

RB=+2J222 References Cited in the file of this patent UNITED STATES PATENTS 660,747 Bausch Oct. 30, 1900 1,463,132 Graf July 24, 1923 1,540,752 Bielicke June 9, 1925 1,739,512 Lee Dec. 17, 1929 I FOREIGN PATENTS 22,157 Great Britain of 1910 299,983 Great Britain Nov. 8, 1928 372,228 Great Britain May 5, 1932 403,706 Germany Oct. 7, 1924 440,229 Germany Feb. 4, 1927 

